This is an update from the joint hearings held Friday by the Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement investigating the causes of the Deepwater Horizon oil rig explosion on April 20.

The Deepwater Horizon had bypassed key alarm and shutdown systems that could have warned the crew on the Deepwater Horizon of impending disaster or may have even guarded against or may have even mitigated some of the disaster that struck April 20.

The staggering revelation came from the testimony Friday of Mike Williams, the chief electronics technician on the Transocean rig.

He told federal investigators that the rig's general alarm and indicator lights were set to "inhibited," meaning they would record high gas levels or fire in a computer, but wouldn't trigger any warning signals.

"When I discovered they were inhibited a year ago I inquired why, and the explanation I got was that from the OIM (the top Transocean official on the rig) on down, they did not want people woken up at 3 a.m. due to false alarms," said Williams, who was responsible for fixing many of the rig's various systems.

Williams said he took his concerns to two fellow rig workers before the accident. "I told them that was unsatisfactory, just not in those words," he said. "They told me they had orders from the OIM and the master that the alarms were to be inhibited."

When gas shot up onto the rig April 20, Williams said an emergency shutdown system, which was supposed to shut off the engines, didn't trip, either. The engines ended up overspeeding by drawing power off the gas and Engine No. 3 exploded, Williams said.

As with the general alarm system, the rig leaders decided to bypass a key system on the blowout preventer control panel that would have cut off the spark source if dangerous gas got in the drill shack, Williams testified. As it turned out, that's where gas apparently shot onto the rig and ignited, killing 11 workers.

Williams said he discovered that about five weeks before the accident while he was trying to fix the gas purging system. He said Mark Hay, the Transocean senior subsea supervisor, set the control panel system to bypass its gas shutdown function, and when Williams questioned him, Hay said there was no point in Williams fixing it because none of the Transocean rigs use the safety system.

"He said, 'Damn thing been in bypass for five years. Matter of fact, the entire (Transocean) fleet runs them in bypass,'" Williams testified.

Williams may have finally provided some clues as to why fluids seeped out through a valve in the well's blowout preventer during a final test of pressure in the well.

About five weeks before the accident, Williams was called to check on a computer system in the drill shack that was constantly on the fritz. Williams said the software was chronically bad, leaving a "blue screen of death" on the driller's interface and often causing the driller to lose crucial data about what was going on in the well. Once, when the Deepwater Horizon was drilling a different well, the computer froze up and the rig took a kick of natural gas while the driller was looking at "erroneous data," Williams said.

While he was trying to deal with the software problem five weeks before the accident, Williams said he saw a contract worker with chunks of rubber that had come up from the well. Williams was disturbed by it because the only rubber in the subsea system would have been the crucial annular valve on the blowout preventer, but Hay told Williams it was no big deal.

Shortly after that, Williams was called into the blowout preventer control area to see why the drill pipe had moved while the annular valve was closed tight around it. He said he discovered a joystick controlling the pipe had been moved inadvertently, and he deduced that the rubber valve must have been damaged at that time.

Transocean attorney Ned Kohnke suggested that Hay and others might have different information to suggest the annular valve was not closed around the pipe when the joystick was moved. Williams insisted that the data he saw indicate the valve was closed.

Hay was supposed to testify before the Marine Board panel on Wednesday but he didn't show up.

On April 20, the drilling team was surprised to find that high pressure wasn't enough to keep the annular valve closed during the negative pressure test. But the rig leaders decided to simply run the test again and, in spite of some confusion, deemed the test a success and OK'd the removal of protective drilling mud that might have stopped the fatal gas bulge.

Williams was among the first rig workers to speak out publicly about what happened on the rig. A few weeks after the accident, he appeared on CBS' "60 Minutes" to tell his story. He is one of only two rig workers to volunteer to be a "party of interest" in the federal investigation, giving his lawyers access to key documents. Other individuals named parties of interest were declared as such by investigators as a result of their conduct.